Investigation of the spatio-temporal flow structure in the buffer region of a turbulent boundary layer by means of multiplane stereo PIV

In order to examine the physical process associated with the production and transport of turbulence in wall bounded flows, a fully developed turbulent boundary layer flow along a flat plate is investigated in stream-wise span-wise planes at y(+)approximate to10, 20, and 30, and Re(theta)approximate to7,800 by using a high-resolution multiplane stereo PIV system. Of particular interest are the structural features of the coherent flow structures, such as their average size and shape, but their intensity, dynamics, and interaction are also examined. The information is deduced from the joint probability density function of the velocity fluctuations and from various correlation, cross-correlation, and conditional-correlation functions. Furthermore, characteristic instantaneous velocity fields are analyzed in order to examine the importance of the individual coherent flow structures for the production of turbulence and the transport of Reynolds stresses.